PROJECT 4 ? PROJECT SUMMARY Hepatocellular carcinoma (HCC) is the second most frequent cause of death from cancer and a lack of effective therapeutic options has led to a 5-year survival rate below 12%. Our group has conducted extensive preclinical characterization of engineered Vesicular Stomatitis Virus (VSV) as an oncolytic platform and has demonstrated it to be a highly effective immunotherapeutic agent for the treatment of cancer. We have established murine models which demonstrate that the combination of systemic checkpoint blockade in conjunction with an intratumorally delivered oncolytic virus can significantly improve survival outcome over either modality alone. In addition to the oncolytic effects of VSV, we developed this platform as a potent vaccine vector that is capable of breaking tolerance to tumor-associated antigens (TAAs) in several mouse tumor models. In the current proposal, we will build on an ongoing Phase I clinical trial for HCC in which oncolytic VSV expressing the immune stimulatory gene Interferon-? (IFN-?) is injected directly into liver cancers, and on our pre-clinical data supporting combinatorial therapy with an immune checkpoint inhibition strategy. The overall hypothesis of the current project is that oncolytic VSV provides a complementary mechanism of action to immune checkpoint inhibition. The combination of VSV- IFN-? with durvalumab (anti- PD-L1) will be tested in a Phase IB clinical study in patients with advanced HCC (Aim 1). Using both murine models of HCC, we we will further refine dosing regimens of rational, mechanism-based, combinations of multiple checkpoint blockade antibodies with VSV-IFN-? (Aim2). Using murine HCC models, will identify and validate novel HCC TAAs that we will target with VSV immunotherapy (Aim 3). Overall, these studies will provide insight into the design of optimized combination therapy and lead to a series of new clinical trials for the treatment this disease for which few effective conventional therapies currently exist.